Currently, the high-end projectors on the market are implemented with multiple lens switchable function, so that a user can purchase one projector only and assembly a particular lens (such as a telephoto lens or short focus lens) into the projector based on the corresponding environment.
In generally, backlight source of high-end projector on the market has a relatively-high illumination; therefore, a user may have his eyes burned by the light with relatively-high illumination when the user directly eyes the projector while switching the lenses of the projector. Thus, to prevent the eyes from being burned by the light with relatively-high illumination, the user must manually turn off the backlight source before switching the lenses. However, turning off the backlight source for each switch of lens is quite bothering process and timing consuming for a user. More seriously, if a user directly disassemblies a lens from the projector without turning off the backlight source in advance, the user may have his eyes burned.
To avoid the aforementioned case, another high-end projector on the market is designed to have a movable light shielding structure, which is disposed at a light-permissive aperture of the projector and for directly covering the light-permissive aperture and thereby automatically blocking the backlight source while a lens is being disassembled from the projector. However, the projector may have a higher cost due to that an additional light shielding structure is required. Further, if an elastic structure (such as a spring) is used for the on/off switch of the movable light shielding structure, a user may still have his eyes burned once the elastic structure has elastic fatigue and cannot completely block the backlight source while switching the lenses.
Therefore, it is quite important to provide a projector capable of automatically blocking the backlight source while a lens is being disassembled from the projector without additional light shielding structure and higher production cost.